hi,
I was looking for something else and stumbled across your post.
I am an electronic Engineer. Your modulation is a slow build up of waves going back and forth, building up much like a bridge collapsing or tsunami building up, wave over wave. You probably are starting with less then 1 hz - you cannot hear this, then increasing until audible range.
I have designed high frequency circuits and networking etc. The signal reflections are causing this and they are caused by "mirrors" in the signal path.
You only bet is to change out each item in your system until you find it. The amp, pre-amp, speaker cable, Interconnect, source etc.
You could try to isolate this by turning on just the amp and speakers, leave it on for 1 day. Try it with just the pre-amp, amp, speaker. Then 1 source, pre-amp, amp, speaker, then another source, pre-amp, amp, speaker until you figure out where in the chain the reflection is.
If you have the reflection jumping across or around the components, then you have a very unique situation - you should write this up. IT is hard, not impossible, for reflections to go backwards through components, it is typically within or between 2 components.
Also, not possible to bench measure, the power supply of one of the units has the slow modulation, so you have to open all the units and measure which unit is creating this modulation when you hear the sound. You will need a scope to see this.
All of this is a lot of work. It might be a lot more fun just to change everything out and start fresh. Unless you type A and have to solve this for enjoyment.
I was looking for something else and stumbled across your post.
I am an electronic Engineer. Your modulation is a slow build up of waves going back and forth, building up much like a bridge collapsing or tsunami building up, wave over wave. You probably are starting with less then 1 hz - you cannot hear this, then increasing until audible range.
I have designed high frequency circuits and networking etc. The signal reflections are causing this and they are caused by "mirrors" in the signal path.
You only bet is to change out each item in your system until you find it. The amp, pre-amp, speaker cable, Interconnect, source etc.
You could try to isolate this by turning on just the amp and speakers, leave it on for 1 day. Try it with just the pre-amp, amp, speaker. Then 1 source, pre-amp, amp, speaker, then another source, pre-amp, amp, speaker until you figure out where in the chain the reflection is.
If you have the reflection jumping across or around the components, then you have a very unique situation - you should write this up. IT is hard, not impossible, for reflections to go backwards through components, it is typically within or between 2 components.
Also, not possible to bench measure, the power supply of one of the units has the slow modulation, so you have to open all the units and measure which unit is creating this modulation when you hear the sound. You will need a scope to see this.
All of this is a lot of work. It might be a lot more fun just to change everything out and start fresh. Unless you type A and have to solve this for enjoyment.